The Federal Energy Regulatory Commission authorized upgrades of turbines for four units -- Units 1, 6, 7, and 8 -- in a 40-year relicense order in 2007. (HNN 4/2/07) FERC amended the project license in December 2008 to revise the authorized installed capacity to reflect the uprating of various turbines and generators.
Voith Siemens Hydro Power Generation provided equipment and services for all four units. AmerenUE upgraded Units 1 and 7 in 2008, increasing the unit capacity to 33.5 MW from 26 MW and improving aeration capability to resolve downstream dissolved oxygen concerns.
Work to upgrade Units 6 and 8 began in September 2008, and also is to increase the capacity of each unit to 33.5 MW while improving aeration.
Osage powerhouse, at Bagnell Dam on the Lake of the Ozarks, is equipped with eight main turbine-generators and two auxiliaries. AmerenUE said it plans to replace turbines in the auxiliary units in fall 2009 to increase flow capacity.
The upgrades should increase the project's maximum hydraulic capacity by 1,580 cubic feet per second, resulting in a 6.5 percent increase in annual generation of about 41,600 megawatt-hours.
In preparing to upgrade turbines in Units 1 and 7 in the fall of 2007, AmerenUE contracted with National Electrical Coil to assess the uprate potential of the eight main generators. The study determined generators for the two units could be upgraded with new turbines, and the six remaining generators could be operated to an 80-degree Centigrade rise without modifying the generators, thus providing a higher capacity rating.
AmerenUE performed generator work while turbines were upgraded for Units 1 and 7: Unit 1 work included re-insulating rotor poles; and Unit 7 work involved re-insulating rotor poles and new stator windings.
Units 3 and 5 were upgraded in 2002, to 33.5 MW from 26 MW. There are no plans to upgrade Units 2 and 4.